The present invention relates to an exhaust valve assembly and, more particularly, to an exhaust valve assembly for controlling the flow of exhaust gases therethrough.
Important considerations in the design of exhaust systems include the muffling of sound, and engine performance. At lower engine RPM, such as occurs at idle or cruising speed, it typically is desirable to have a higher back pressure in the exhaust system to help muffle the exhaust sound and create a quieter exhaust. At higher RPM, when engine performance is desired, it typically is desirable to have lower back pressure in the exhaust system to obtain higher horsepower engine performance. At higher RPM, though, the increased exhaust flow triggers the exhaust valve to open, which reduces back pressure.
Many efforts have been made in the design of exhaust systems to address these important considerations. One known exhaust valve system that has been relatively successful in the marketplace, for example, uses a hinged flap and a linear torsion spring that connects the flap to the exhaust pipe and extends across the open end of the exhaust tube. The spring exerts a closing force on the flap that increases as the valve opens. A drawback of this and other known systems is that the closing force exerted on the flap increases substantially as the flap opens which tends to increase back pressure.
It is an object of the present invention to provide an exhaust valve system having a flap that opens once the engine reaches a predetermined RPM.
It is a further object of the present invention to provide an exhaust valve system that applies a closing force on the flap that increases in magnitude at a non-linear rate as the flap opens.
It is another object of the present invention to provide an exhaust valve system that uses a linear spring to apply a non-linear closing force on the flap.
In accordance with these and other objects, the present invention provides an exhaust valve assembly for controlling the flow of exhaust. The exhaust valve assembly comprises a hollow elongated member, desirably in the form of an exhaust pipe or component thereof, for the flow of gas therethrough. The hollow elongated member has an open end, and the exhaust valve assembly further comprises a flap associated with the open end and a spring having two ends. The flap is pivotable between a first position to close the open end and a second position to open the open end, and is adapted to pivot toward the second position when the exhaust gas within the elongated member achieves a predetermined pressure. One end of the spring is associated with the flap and the other end of the spring is associated with the elongated member along the length of the elongated member. The spring biases the flap toward the first position. The spring desirably extends generally parallel to a longitudinal axis of the elongated member when the flap is in the first position. The flap desirably includes a lateral edge having a hook and the one end of the spring is mounted to the hook.
In a preferred embodiment, the exhaust valve assembly further includes a magnet associated with the open end of the elongated member for biasing the flap toward the first position when the pressure of exhaust gas within the elongated member is less than a predetermined level. The magnet desirably prevents rattling of the flap and maintains the flap in a closed position at low exhaust gas pressure. Additionally, the flap may include an enclosing portion and a distal portion and the hollow elongated member may include a flange for engaging the distal portion when the flap is in the first position. The magnet desirably applies the biasing force to the distal portion. The spring may be a coil spring, a bent wire spring or any other type of spring.
In a preferred embodiment, the flap is hingedly connected to the elongated member in any suitable manner. For example, the elongated member may define a pair of holes to receive a stem that is rigidly mounted to the flap. Additionally, the elongated member desirably is a single piece extrusion.
Other objects, advantages and novel features of the present invention will become apparent from the following detail description of the drawings when considered in conjunction with the accompanying drawings.